Uplink grant, downlink assignment and search space method and apparatus in carrier aggregation

ABSTRACT

Methods of mapping, indicating, encoding and transmitting uplink (UL) grants and downlink (DL) assignments for wireless communications for carrier aggregation are disclosed. Methods to encode and transmit DL assignments and UL grants and map and indicate the DL assignments to DL component carriers and UL grants to UL component carriers are described. Methods include specifying the mapping rules for DL component carriers that transmit DL assignment and DL component carriers that receive physical downlink shared channel (PDSCH), and mapping rules for DL component carriers that transmit UL grants and UL component carriers that transit physical uplink shared channel (PUSCH) when using separate coding/separate transmission schemes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/027,814, filed Sep. 22, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/423,567, filed May 28, 2019, which issued asU.S. Pat. No. 10,785,768 on Sep. 22, 2020, which is a continuation ofU.S. patent application Ser. No. 15/795,896, filed Oct. 27, 2017, whichissued as U.S. Pat. No. 10,306,620 on May 28, 2019, which is acontinuation of U.S. patent application Ser. No. 14/673,538, filed Mar.30, 2015, which issued as U.S. Pat. No. 9,820,269 on Nov. 14, 2017,which is a continuation of U.S. patent application Ser. No. 13/654,182,filed Oct. 17, 2012, which issued as U.S. Pat. No. 8,995,376 on Mar. 31,2015, which is a divisional of U.S. patent application Ser. No.14/723,308 filed Mar. 12, 2010, which claims the benefit of U.S.Provisional Application No. 61/160,167 filed Mar. 13, 2009, the contentsof which are hereby incorporated by reference herein.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

Long Term Evolution (LTE) supports data rates up to 100 Mbps in thedownlink and 50 Mbps in the uplink. LTE-Advanced (LTE-A) provides afivefold improvement in downlink data rates relative to LTE using, amongother techniques, carrier aggregation. Carrier aggregation may support,for example, flexible bandwidth assignments up to 100 MHz. Carriers areknown as component carriers in LTE-A. A wireless transmit/receive unit(WTRU) may simultaneously receive one or more component carriers.

LTE-A may operate in symmetric and asymmetric configurations withrespect to component carrier size and the number of component carriers.This is supported through the use or aggregation of up to five 20 MHzcomponent carriers. For example, a single contiguous downlink (DL) 40MHz LTE-A aggregation of multiple component carriers may be paired witha single 15 MHz uplink (UL) component carrier. Non-contiguous LTE-A DLaggregate carrier assignments may therefore not correspond with an ULaggregate carrier grant.

Aggregate carrier bandwidth may be contiguous where multiple adjacentcomponent carriers may occupy continuous 10, 40 or 60 MHz. Aggregatecarrier bandwidth may also be non-contiguous where one aggregate carriermay be built from more than one, but not necessarily adjacent componentcarriers. For example, a first DL component carrier of 15 MHz may beaggregated with a second non-adjacent DL component carrier of 10 MHz,yielding an overall 25 MHz aggregate bandwidth for LTE-A. Moreover,component carriers may be situated at varying pairing distances. Forexample, the 15 and 10 MHz component carriers may be separated by 30MHz, or in another setting, by only 20 MHz. As such, the number, sizeand continuity of component carriers may be different in the UL and DL.

In LTE, WTRUs receive their data (and in some cases their controlinformation) on the physical downlink shared channel (PDSCH). Thetransmission of the PDSCH is scheduled and controlled by the basestation using the so-called downlink scheduling assignment, which iscarried on physical downlink control channel (PDCCH). As part of thedownlink scheduling assignment, the WTRU receives control information onthe modulation and coding set (MCS), downlink resources allocation(i.e., the indices of allocated resource blocks), and other similarinformation. Then, if a scheduling assignment is received, the WTRU willdecode its allocated PDSCH resources on the correspondingly allocateddownlink resources.

In LTE-A, PDSCH(s) to a given WTRU may be transmitted on more than oneassigned component carrier and multiple approaches for allocating PDSCHresources on more than one component carrier may exist.

In LTE-A, the PDCCHs or Downlink Control Information (DCI) messagescontained therein carrying the assignment information may be separatelytransmitted for the component carriers containing the accompanying PDSCHtransmissions. For example, if there are 2 component carriers, there are2 separate DCI messages on each component carrier corresponding to thePDSCH transmissions on each component carrier respectively.Alternatively, the 2 separate DCI messages for the WTRU may be sent onone component carrier, even though they may pertain to accompanyingdata, or PDSCH transmissions on different component carriers. Theseparate DCI messages of the PDCCHs for a WTRU or a group of WTRUs maybe transmitted in one or in multiple component carriers, and may nottransmit all of the PDCCHs on every component carrier. For example, afirst DCI transmission on the PDCCH pertaining to the PDSCH allocationon a first component carrier may also be contained on this firstcomponent carrier, but the second DCI to that WTRU PDCCH transmissionpertaining to the PDSCH allocation on a second component carrier may becontained on this second component carrier.

The DCI carrying the assignment information for PDSCH(s) on more thanone component carrier may be encoded jointly and carried by one singlejoint DCI control message, or PDCCH message. For example, a single DCIor PDCCH or control message carrying an assignment of PDSCHs or dataresources on two component carriers may be received by the WTRU. Inanother example, the joint PDCCH for a WTRU or group of WTRUs may betransmitted in one or multiple component carriers.

In LTE-A with carrier aggregation, different PDCCH assignments, codingor allocation schemes represent distinct technical advantages. Both ULgrants and DL assignments may be carried by PDCCHs. Due to asymmetriccarrier aggregation, PDCCH methods that may be suitable for DLassignments may not be suitable for UL grants. Furthermore, PDCCHmethods that are suitable for some configurations or assignments/grantsof carrier aggregation may not be suitable for other configurations orassignments/grants of carrier aggregation. For example, in an asymmetriccarrier aggregation in which there are more UL component carriers thanDL component carriers, a separate PDCCH may be directly used for DLassignment because there exists one-to-one mapping between a DL carrierand the DL carrier that transmits the DL assignment. In other words, aDL assignment that may be transmitted in DL component carrier x carriescontrol information for DL component carrier x. However, in this caseseparate PDCCH may not be directly used for UL grants because there aremore UL component carriers than DL component carriers. This is also truein the case of asymmetric carrier aggregation where more DL componentcarriers than UL component carriers are used. In addition, whendifferent encoding and transmission schemes are used, how UL grants aremapped to UL component carriers and DL assignments to DL componentcarriers should be specified.

Methods to associate or map the DL assignment to DL component carrierand UL grant to UL component carrier are desired. This may beparticularly true when asymmetric carrier aggregation, UL grants anddifferent encoding/transmission schemes are considered. Optimal methodsthat are suitable for separate or joint DL assignments and UL grants aredesirable.

SUMMARY

Methods of mapping, indicating, encoding and transmitting uplink (UL)grants and downlink (DL) assignments for wireless communications forcarrier aggregation are disclosed. Methods to encode and transmit DLassignments and UL grants and map and indicate the DL assignments to DLcomponent carriers and UL grants to UL component carriers are described.Methods include specifying the mapping rules for DL component carriersthat transmit DL assignment and DL component carriers that receivephysical downlink shared channel (PDSCH), and mapping rules for DLcomponent carriers that transmit UL grants and UL component carriersthat transit physical uplink shared channel (PUSCH) when separatecoding/separate transmission schemes are used. Methods also includeusing radio network temporary identification (RNTI), special physicaldownlink control channel, carrier ID, detection orders, dedicated searchspace mapping to component carriers and other methods to indicate,implicitly or explicitly, DL/UL component carriers when separatecoding/joint transmission and joint coding/joint transmission are used.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1 is an embodiment of a wireless communication system/accessnetwork of long term evolution (LTE) and/or LTE-Advanced (LTE-A);

FIG. 2 are example block diagrams of a wireless transmit/receive unit(WTRU) and a base station of the LTE and/or LTE-A wireless communicationsystem;

FIG. 3 shows an example of wireless communications using componentcarriers;

FIG. 4 shows an example flowchart for WTRU procedures in a mappingmethod for an example asymmetric component carrier configuration;

FIG. 5 shows an example flowchart for WTRU procedures if N cell-radionetwork temporary identifiers are used to indicate N component carriersin either uplink or downlink direction;

FIGS. 6A and 6B show an example flowchart of cross component carrierpower control using transmit power control (TPC) physical uplink sharedcontrol channel (PUSCH) radio network temporary identifier (RNTI)(TPC-PUSCH-RNTIs), TPC physical uplink control channel (PUCCH)(TPC-PUCCH-RNTIs) or both;

FIG. 7 shows an example flowchart for using detection position or searchspace partition to indicate component carriers;

FIG. 8 shows an example block diagram of the relationship betweencomponent carriers and dedicated search spaces and cross carrierscheduling;

FIG. 9 shows another example flowchart for using detection position orsearch space partition to indicate component carriers; and

FIG. 10 shows an example block diagram of the relationship betweencomponent carriers and dedicated search spaces and cross carrierscheduling with limited scheduling capability.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, evolved Node-B (eNB), a site controller, anaccess point (AP), or any other type of interfacing device capable ofoperating in a wireless environment.

In long term evolution-advanced (LTE-A) with carrier aggregation,different physical downlink control channel (PDCCH) assignment, codingor allocation schemes represent distinct technical advantages. Bothuplink (UL) grants and downlink (DL) assignments may be carried by thePDCCH. Due to asymmetric carrier aggregation, PDCCH methods that may besuitable for DL assignments may not be suitable for UL grants.Furthermore, PDCCH methods that are suitable for some configurations orassignments/grants of carrier aggregation may not be suitable for otherconfigurations or assignments/grants of carrier aggregation. Forexample, in an asymmetric carrier aggregation in which there are more ULcomponent carriers than DL component carriers, separate PDCCH may bedirectly used for DL assignment because there exists one-to-one mappingbetween a DL carrier and the DL carrier that transmits the DLassignment. In other words, a DL assignment that may be transmitted inDL component carrier x carries control information for DL componentcarrier x. However, in this case a separate PDCCH may not be directlyused for UL grants because there are more UL component carriers than DLcomponent carriers. This is also true for asymmetric carrier aggregationwhen more DL component carriers than UL component carriers are used. Inaddition, when different encoding and transmission schemes are used, howUL grants are mapped to UL component carriers and DL assignments to DLcomponent carriers should be specified.

In order to illustrate the methods, different PDCCH methods may becategorized according to how they are encoded and how they aretransmitted. Suppose there are DL component carriers and downlinkcontrol information (DCI) #n is the DL control information for carriern. Each DCI may be encoded separately from other DCIs and each may becarried in a PDCCH. They may also be encoded jointly. That is, all DCIn, n=1, 2 . . . N may be encoded together into a single joint DCI with alarger size and may be carried in a single joint PDCCH. After encoding,each PDCCH carrying a DCI may be transmitted in separate DL componentcarriers or all PDCCHs may be transmitted jointly in one componentcarrier. When DCIs are encoded separately, it may be referred to as“separate coding” and if they are encoded jointly, it may be referred toas “joint coding”. When a PDCCH carrying a DCI is transmitted separatelyin different component carriers, it may be referred to as “separatetransmission”. If some or all PDCCHs corresponding to some or allcomponent carriers, respectively, are transmitted all together in onecomponent carrier, it may be referred to as “joint transmission”. Basedon the combinations of how PDCCHs are encoded and transmitted, severalschemes may be possible such as, but not limited to, separatecoding/separate transmission, separate coding/joint transmission, orjoint coding/joint transmission.

The separate coding/separate transmission PDCCH method provides muchflexibility in terms of possible resource assignments. However, thismethod may not exploit possible coding gain achievable from jointcoding. It also may not exploit the power savings possible from havingWTRUs monitor PDCCHs on fewer DL component carriers.

The joint coding/joint transmission PDCCH method may result inrestrictions regarding allocation flexibility due to the sameconsiderations with respect to payload and mapping into the ControlRegion. However, this method may result in less overhead and lower WTRUblind detection complexity. Note that this is particularly important forpower consumption considerations because joint coding/joint transmissionPDCCH method may allow the WTRU to monitor only one DL carrier componentat a time. Also, the joint PDCCH approach may suffer from excessiveoverhead when the number of component carriers used for a specifictransmission is low.

Methods to associate or map the DL assignment to DL component carrierand UL grant to UL component carrier are desired. FIG. 1 shows a LongTerm Evolution (LTE) and/or LTE-Advanced (LTE-A) wireless communicationsystem/access network 100 that includes an Evolved-Universal TerrestrialRadio Access Network (E-UTRAN) 105. The E-UTRAN 105 includes severalevolved Node-Bs, (eNBs) 120. The WTRU 110 is in communication with aneNB 120. The WTRU 110 and eNB 120 may communicate using uplink componentcarriers 150 and downlink component carriers 160. The eNBs 120 interfacewith each other using an X2 interface. Each of the eNBs 120 interfaceswith a Mobility Management Entity (MME)/Serving GateWay (S-GW) 130through an S1 interface. Although a single WTRU 110 and three eNBs 120are shown in FIG. 1, it should be apparent that any combination ofwireless and wired devices may be included in the wireless communicationsystem access network 100.

FIG. 2 is an example block diagram of an LTE or LTE-A wirelesscommunication system 200 including the WTRU 110, the eNB 120, and theMME/S-GW 130. As shown in FIG. 1, the WTRU 110 is in communication withthe eNB 120 and both are configured to perform a method wherein uplinktransmissions from the WTRU 110 are transmitted to the eNB 120 usingmultiple component carriers 250, and downlink transmissions from the eNB120 are transmitted to the WTRU 110 using multiple downlink componentcarriers 260. As shown in FIG. 2, the WTRU 110, the eNB 120 and theMME/S-GW 130 are configured to perform mapping, indicating, encoding andtransmitting of UL grants and DL assignments and searching spaces forwireless communications for carrier aggregation.

In addition to the components that may be found in a typical WTRU, theWTRU 110 includes a processor 216 with an optional linked memory 222, atleast one transceiver 214, an optional battery 220, and an antenna 218.The processor 216 is configured to perform mapping, indicating, encodingand transmitting of UL grants and DL assignments and searching spacesfor wireless communications for carrier aggregation. The transceiver 214is in communication with the processor 216 and the antenna 218 tofacilitate the transmission and reception of wireless communications. Incase a battery 220 is used in the WTRU 110, it powers the transceiver214 and the processor 216.

In addition to the components that may be found in a typical eNB, theeNB 120 includes a processor 217 with an optional linked memory 215,transceivers 219, and antennas 221. The processor 217 is configured toperform mapping, indicating, encoding and transmitting of UL grants andDL assignments and searching spaces for wireless communications forcarrier aggregation. The transceivers 219 are in communication with theprocessor 217 and antennas 221 to facilitate the transmission andreception of wireless communications. The eNB 120 is connected to theMME/S-GW 130 which includes a processor 233 with an optional linkedmemory 234.

FIG. 3 shows an example of multiple component carriers being transmittedand received between eNB 300 and WTRU 305. For example, the multiplecomponent carriers may include downlink component carrier 1 310,downlink component carrier 2 320, uplink component carrier 1 315 anduplink component carrier 2 325. Downlink component carrier 1 310 anddownlink component carrier 2 320 may carry PDCCH(s) that carry downlinkcontrol information (DCI) as described herein.

Mapping rules described herein may be generalized and other mapping andassociation between UL component carriers and DL component carriers thattransmit UL grants and DL assignments may be used. Such mapping rulesmay be signalled, configured or predetermined.

Described herein are example unified methods for UL grants and DLassignments. In a first unified method, separate coding and separatetransmission may be used.

For DL assignments, a one-to-one mapping may be defined between the DLcomponent carrier and the DL component carrier that transmits the DLassignment. An example mapping rule may be that a DL assignmenttransmitted in DL component carrier x carries control information for DLcomponent carrier z, where z=x. This method may work for DL assignmentsregardless of symmetric or asymmetric carrier aggregation.

For UL grants, a one-to-one mapping may be defined between the ULcomponent carriers and the DL component carriers that transmit ULgrants. An example mapping rule may be that an UL grant transmitted inDL component carrier y carries control information for UL componentcarrier z, where z=f(y) and f(*) is a fixed mapping function thatassociates the UL and DL component carriers. This method may work for asymmetric number of component carriers in the UL and DL provided f(*) isknown to both the WTRU and the base station.

For UL grants with asymmetric carrier aggregation, where asymmetryrefers to the number of UL and DL component carriers, additional mappingrules may be required to clearly identify the association between an ULgrant and UL component carrier. In the asymmetric case where there aremore DL component carriers than UL component carriers, there may be anonto function f(*) such that for each UL component carrier there is atleast one DL component carrier that carries UL grants for it. An examplemapping rule f(*) may be that an UL grant transmitted in DL componentcarrier y1, y2 and so on carries control information for UL componentcarrier z1, UL grant transmitted in DL component carrier y3, y4 and soon carries control information for UL component carrier z2 and so on.

Alternatively, the following rule or method may be used where DLcomponent carriers may be made symmetric to UL component carriers for ULgrant purposes. In this method, a subset of DL component carriers may beselected and the number of DL component carriers in the selectedcomponent carrier subset may be set equal to the number of UL componentcarriers. Such a component carrier subset may be signalled, configuredor predetermined.

In the case where there are more UL component carriers than DL componentcarriers, there may be no such onto function but other rules may be usedto make UL grants for all UL component carriers. An example mapping rulemay be that an UL grant transmitted in DL component carrier y1 carriescontrol information for UL component carriers z1, z2 . . . , UL granttransmitted in DL component carrier y2 carries control information forUL component carriers z3, z4 . . . , and so on. In this case, the sameUL grant (thus same control information) may be shared by two or more ULcomponent carriers. In other words, the resource allocation or othercontrol information in the UL grant may be applied to more than one ULcomponent carrier. For example, if the two such UL component carriershave the same bandwidth (BW), the resource allocation for both ULcomponent carriers may be either identical or shifted with a fixedoffset which may be configurable. If they do not have the same BW, theresource allocation may be scaled relative to the BW of a particular ULcomponent carrier e.g., by adjusting the resource granularity forresource allocation. Alternatively, a rule that only component carriershaving the same BW may share the same UL grant may be applied.

Similarly, the above described approach may be applied to the DLassignment for DL component carriers when the DL assignment is shared bymore than one DL component carrier.

The control information payload size may be adjusted to reduce controlchannel blind decoding complexity. WTRU may be required to monitor onlya single payload size control channel format or DCI format instead oftwo different payload size DCI formats for component carriers havingdifferent BWs. The resource allocation may be scaled relative to the BWof a particular DL component carrier. The resource granularity orresource block group (RBG) granularity for resource allocation may beadjusted such that the number of bits for resource allocation is thesame if they do not have the same BW. This may be applicable to DLassignments or UL grants that may or may not be shared by multiplecomponent carriers.

In this asymmetric case, where there are more UL component carriers thanDL component carriers, FIG. 4 illustrates an example flowchart 400 forWTRU procedures using this mapping method. First, the WTRU searchesthrough common search space and WTRU-specific search space of DLcomponent carrier y1 for a PDCCH candidate (405). Second, a PDCCHcandidate is determined. A PDCCH candidate is one where the cyclicredundancy code (CRC) matches the WTRU cell radio network temporaryidentifier (C-RNTI), temporary C-RNTI, semi-persistent RNTI (SPS-RNTI)or other RNTIs that may be used to schedule uplink transmission and DCIformat 0 or other UL DCI format (410). If CRC does not match, searchingis continued (415). If CRC does match, then the DCI format 0 or other ULDCI format defines the uplink grant for uplink shared channel (UL-SCH)of both UL component carrier z1 and z2 (420). In this context, the grantfor both UL component carriers may define the same physical resourceblocks (PRBs), that is the same frequency allocation, if they have thesame BW.

A variant to this method may use a new DCI format 0 or other UL DCIformat for LTE-A where a binary field may define whether the DCI formatreceived applies to all mapped UL component carriers or a subset ofcomponent carriers. In this example, a 2 bit field may inform the WTRUthat DCI format allocation applies to component carrier z1, componentcarrier z2 or both. The 2-bit field may also indicate the number ofother component carriers taken from an ordinal set to use in the ULtransmission, e.g., use a component carrier group taken from the set((c1), (c1,c2), (c1,c2,c3), (c1,c2,c3,c4)), where c1,c2,c3,c4 arepointers to 4 component carriers provided by default or from thenetwork. Such information may also be configured via higher layersignalling.

Alternatively, different RNTIs may be used to indicate a differentset(s) of UL component carriers to use. For example, a WTRU may checkfor which of a set of possible RNTIs it has been addressed with, whichin turn indicates which component carriers to use or which set ofcomponent carriers to use.

The mapping of DL component carrier with UL component carriers may besemi-static and defined by a radio resource controller (RRC) messageduring initial carrier configuration or at some later stage or event.The asymmetric case may take advantage of using a new RRC message thatmay configure one or more component carriers in only one direction,either UL or DL. For example, in the case described herein, an initialRRC message may map DL component carrier y1 with UL component carrierz1. But subsequently, an RRC message may configure an additional ULcomponent carrier z2 and map it to an existing configured DL componentcarrier, such as y1.

In a second unified method, separate coding and joint transmission maybe used. Each DL assignment and UL grant may be separately encoded butjointly transmitted in an anchor component carrier, primary componentcarrier or other component carrier designated for the WTRU to monitor.An anchor or primary component carrier may be a component carrier whichthe WTRU monitors and in which the WTRU receives the DL assignment or ULgrant. Because grants/assignments are transmitted jointly in onecomponent carrier, there may be no one-to-one mapping between thecomponent carrier and the component carrier that transmits the UL grantor DL assignment. RNTIs, carrier IDs or other similar designations orindicators may be used, either implicitly or explicitly, per DLassignment or UL grant to map DL assignment to DL component carrier orUL grant to UL component carrier.

In one indication method, RNTIs may be used to indicate the componentcarriers. For each UL grant or DL assignment, the PDCCH may be maskedwith, for example, C-RNTI #n, n=1, 2, . . . , N, to indicate which UL orDL component carrier corresponds to which UL grant or DL assignment,respectively. In this case, N is the number of maximum componentcarriers in one direction. PDCCH masked with C-RNTI#n may carry controlinformation for component carrier n in UL or DL.

FIG. 5 shows an example flowchart 500 that a WTRU may use if N C-RNTIsare used to indicate N component carriers for either UL, DL or both.First, a WTRU may decode and de-mask all C-RNTIs (505). If C-RNTI#npasses the CRC test (510), then PDCCH masked with C-RNTI#n is forcomponent carrier n (520). If C-RNTI#n does not pass the CRC test, thentry another component carrier C-RNTI or CRC (515). This exampleprocedure may be applicable to both UL grants and DL assignments.Although a C-RNTI is shown in FIG. 5, the other RNTIs described hereinmay be used.

In the C-RNTI example, each WTRU may be assigned C-RNTIs for eachcomponent carrier. C-RNTIs may be reused for WTRUs. To avoid overlap ofsearching space or collision of C-RNTIs, WTRUs that have same oroverlapping assigned C-RNTIs may be assigned with different downlinkanchor or primary component carriers. To balance the signalling load,WTRU-specific downlink anchor or primary component carrier may be used.To relax scheduling restrictions, each WTRU may have unique C-RNTIs. Theavailability analysis for C-RNTIs is described later herein. In additionto the C-RNTI, SPS-C-RNTI, temporary C-RNTI, or other appropriate RNTIsmay be used.

In an illustrative example, suppose the DL component carriers areCarrier 1D, Carrier2D, Carrier3D and the UL component carriers areCarrier 1U and Carrier2U. In this case, N is 3 for DL or N is 2 for UL.Three different C-RNTI, SPS-C-RNTI or other similar RNTI may be requiredto indicate which DL component carrier the DCI is applicable for and 2different C-RNTI, SPS-C-RNTI or other similar RNTI may be required toindicate which uplink component carrier the DCI format is applicable to.For example, C-RNTI#1, C-RNTI#2, and C-RNTI#3 may be used to indicatewhich downlink component carrier #1, #2 or #3 the DCI format isapplicable to. C-RNTI#1 and C-RNTI#2 may be used to indicate whichuplink component carrier #1 or #2 the DCI format is applicable to.

In another example, power-control messages may be directed to a group ofWTRUs using an RNTI specific for that group. Each WTRU may be allocatedtwo power-control RNTIs, one for physical uplink control channel (PUCCH)power control and the other for physical uplink shared channel (PUSCH)power control. The transmit power control PUSCH RNTI (TPC-PUSCH-RNTI) isthe identification used for the power control of PUSCH and the transmitpower control PUCCH RNTI (TPC-PUCCH-RNTI) is the identification used forthe power control of PUCCH. Although the power control RNTIs are commonto a group of WTRUs, each WTRU may be informed through RRC signalingwhich TPC bit(s) in the DCI message it should follow. TheTPC-PUSCH-RNTI, TPC-PUCCH-RNTI or both may be used to indicate thecomponent carriers.

Two different TPC-PUSCH-RNTIs and/or two different TPC-PUCCH-RNTIs maybe required to indicate to which uplink component carrier the DCI formatfor power control is applicable to. A new TPC-PUSCH-RNTI orTPC-PUCCH-RNTI would be assigned for each additional uplink componentcarrier. As described herein, when adding an UL component carrier, anadditional RNTI may be added. However, the RNTIs used for indication ofDL component carriers may be reused for indication of UL componentcarriers. This is not the case for TPC-PUSCH-RNTI or TPC-PUCCH-RNTIwhich are for UL component carriers only.

FIGS. 6A and 6B show an example flowchart 600 of cross component carrierpower control using TPC-PUSCH-RNTIs, TPC-PUCCH-RNTIs or both. WTRUdecodes PDCCH DCI format 3 or 3A with TPC-PUSCH-RNTIs, TPC-PUCCH-RNTIsor both (605). If it is a TPC-PUSCH-RNTI, the WTRU checks if theTPC-PUSCH-RNTI passes the CRC test (610). If the CRC test fails,searching is continued (612). If the CRC check passes for theTPC-PUSCH-RNTI, then the TPC-PUSCH-RNTI indicates that the decoded DCIformat 3 or 3A information, e.g., transmit power control, is associatedwith UL component carrier n, where n=1, 2, 3 and so on (615). The WTRUextracts the transmit power control (TPC) commands from DCI format 3 or3A (620). If DCI format 3 was sent, then the TPC command is a two bitpower adjustment field and if DCI format 3A was sent, then the TPCcommand is an one bit power adjustment field. Since DCI format 3 or 3Acarries multiple power control commands for a group of WTRUs, the WTRUneeds to know which TPC command is applicable to the specific WTRU. Thisis generally configured by higher layer signalling, e.g., RRCsignalling. In one example, the WTRU uses the parameter tpc-Index, whichis sent by higher layers, to determine the index to the TPC command forthe specific WTRU (625). The WTRU then adjusts the transmit power of thePUSCH in uplink component carrier n according to the TPC commandreceived for this WTRU in the corresponding DCI format 3/3A (630). WTRUcontinues search for PDCCH DCI format 3/3As with TPC-PUSCH-RNTIs forother UL component carriers (633).

If it is a TPC-PUCCH-RNTI, the WTRU checks if the TPC-PUCCH-RNTI passesthe CRC test (635). If the CRC test fails, searching is continued (637).If the CRC check passes for the TPC-PUCCH-RNTI, then the TPC-PUCCH-RNTIindicates that the decoded DCI format 3 or 3A information, e.g.,transmit power control, is associated with UL component carrier n, wheren=1, 2, 3 and so on (640). The WTRU extracts the transmit power control(TPC) commands from DCI format 3 or 3A (645). As noted above, if DCIformat 3 was sent, then the TPC command is a two bit power adjustmentfield and if DCI format 3A was sent, then the TPC command is an one bitpower adjustment field. Again as noted above, the WTRU needs to knowwhich TPC command is applicable to the specific WTRU. In one example,the WTRU uses the parameter tpc-Index, which is sent by higher layers,to determine the index to the TPC command for the specific WTRU (650).The WTRU then adjusts the transmit power of the PUCCH in uplinkcomponent carrier n according to the TPC command received for this WTRUin the corresponding DCI format 3/3A (655). WTRU continues search forPDCCH DCI format 3/3As with TPC-PUCCH-RNTIs for other UL componentcarriers (660).

In another example, the WTRU may be assigned a C-RNTI_1 for Carrier 1Dand Carrier 1U, C-RNTI_2 for Carrier 2D and Carrier 2U and C-RNTI_3 forCarrier 3D. Assuming that Carrier2D is an anchor or primary componentcarrier, the WTRU evaluates a PDCCH candidate on Carrier2D. The WTRUthen checks for each PDCCH candidate for different DCI format lengthwith address C-RNTI_1, C-RNTI_2 and C-RNTI_3. If PDCCH candidate's CRCmatched with C-RNTI_2 and the PDCCH is DCI format 0, then the receiveduplink scheduling grant in DCI format 0 is applicable to Carrier2U. IfPDCCH candidate's CRC matched with C-RNTI_1 and the PDCCH is DCI format0, then the received uplink scheduling grant in DCI format 0 isapplicable to Carried U.

Anchor or primary component carriers may be used separately for DLassignments and UL grants. To further balance signalling load and reducethe use of C-RNTIs, DL assignments and UL grants may be transmitted intwo different anchor or primary component carriers. That is, one anchoror primary component carrier for DL assignment (DL assignment specificanchor/primary component carrier) and one anchor or primary componentcarrier for UL grant (UL grant specific anchor/primary componentcarrier). They may also be WTRU-specific. Each WTRU may be assigned, forexample, C-RNTIs for corresponding UL/DL component carriers.

Alternatively, a RRC message to reassign WTRU to another anchor orprimary component carrier may be useful not only for control regioncapacity load balancing but also in the context of sharing addresses.Also, dedicated signalling reassigning the anchor or primary componentcarrier may include for example C-RNTI re-assignment.

In another indication method, detection orders may be used to indicatecomponent carriers. In this method, DL assignment to DL componentcarrier or UL grant to UL component carrier may be mapped based on thedetection order of DL assignment or UL grant. Detection orders arespecified such that there may be no ambiguity regarding the detectionorder. The rules for the sequence of detection based on control channelelement (CCE) aggregation level (e.g., from highest to lowest level orfrom lowest to highest level), CCE addresses (e.g., start from address0), search space, or other similar procedures may be defined orspecified. Such rules are known to the base station and WTRU bypredetermination, RRC configuration or L1/2 and RRC signalling. Themapping between detection order and carrier may be that the firstdetected DL assignment is for the first assigned DL component carrier,the second detected DL assignment is for the second assigned DLcomponent carrier and so on. Similarly for the UL grant and UL componentcarrier, the mapping between detection order and component carrier maybe that the first detected UL grant is for the first assigned ULcomponent carrier, the second detected UL grant is for the secondassigned UL component carrier and so on. The information about whichDL/UL component carriers are assigned may be signalled. In this case, noRNTI or carrier ID in DL assignment or UL grant to indicate componentcarriers may be required. The reliability of this successive method maybe increased by using large CCE aggregation level for the first fewPDCCHs.

In another indication method, detection position such as search spacepartition or dedicated search space (or extended dedicated search space)corresponding to component carriers may be used to indicate componentcarriers. DL assignment to DL component carrier or UL grant to ULcomponent carrier may be mapped based on the detection position, searchspace partition or dedicated search space (corresponding to componentcarriers) of the PDCCH carrying DL assignment or UL grant. Differentpotential search spaces, search space partitions or dedicated searchspaces (either the same or extended search space as in LTE) aredesignated for different component carriers. The partitioning of thesearch space may be cell specific or WTRU specific. In this way, theWTRU learns the component carrier to be used from the position of thePDCCH (the dedicated search space or search space partitions where thePDCCH is detected). Furthermore, the WTRU may receive additionalsignalling to reduce the space that it must search to detect anypossible PDCCH (e.g., a low data rate WTRU may be told to only searchthe PDCCH search space that could carry single component carriergrants).

Search space may be partitioned with respect to the LTE search space ornew search space such that the PDCCH blind decoding complexity may bereduced due to a smaller search space. Search space may be dedicated tocomponent carriers and the dedicated search space may be extended orexpanded such that the PDCCH block probability may be reduced due to alarger search space. LTE search space may also be used such that thereare multiple LTE search spaces in each component carrier for a givenWTRU, and each of the search spaces is dedicated for a componentcarrier. This is illustrated in FIGS. 8 and 10, which are described inmore detail below.

The search space may be predefined or fixed by system definition.Alternatively, the search space may be configured or signalled by higherlayers using, for example, RRC signalling or a broadcast channel systemconfiguration message or element. In one example, a search space isdefined as a set of candidate control channels (PDCCHs) formed by theset of control channel elements (CCEs) for a given aggregation levelwhich the WTRU is supposed to monitor or decode. A specific PDCCH isidentifiable by the numbers of the corresponding CCEs in the controlregion. This is then used to determine or map to the component carrier.

FIG. 7 shows an example detection position flowchart 700 for usingsearch space partitions or dedicated search spaces to indicate componentcarriers and FIG. 8 shows an example block diagram of the relationshipbetween the component carriers and dedicated search spaces and crosscarrier scheduling. Referring to FIG. 7, the WTRU searches dedicatedsearch spaces or search space partitions for a PDCCH candidate (705).The WTRU decodes PDCCH DCI formats with RNTIs (710) and then determinesif the DCI format has been correctly decoded (715). If not, the WTRUtries another CRC or RNTI (720). If all the DCI formats have beencorrectly decoded, then for each correctly decoded DCI format, the WTRUuses the information with respect to where the PDCCH was detected todetermine the relevant component carrier (725). The WTRU then uses theDCI information to receive the PDSCH or transmit the PUSCH (730). Thisis then repeated for the additional search space segments in theidentified component carrier using the same RNTIs (735). Alternatively,the WTRU may search the search spaces in a parallel fashion.

The DCI information may allow cross carrier scheduling such that the DCI(in the PDCCH) in a component carrier (say CC x) may schedule PDSCH (orPUSCH) in a different component carrier (say CC y), where CC x may notbe equal to CC y.

As shown in FIG. 8, each component carrier may have dedicated searchspaces (SS) in a control region (PDCCH) corresponding to multiplecomponent carriers. For example, in the control region of componentcarrier 1 (CC1) there are dedicated SSs for CC1, CC2, CC3, . . . , i.e.,CC1 SS is for PDSCH (or PUSCH) of CC1, CC2 SS is for PDSCH (or PUSCH) ofCC2, CC3 SS is for PDSCH (or PUSCH) of CC3. The WTRU only searches CC nSS for CC n, where n=1, 2, 3, . . . and SS is not shared betweencomponent carriers.

FIG. 9 shows an example detection position flowchart 900 for usingsearch space partitions or dedicated search spaces to indicate componentcarriers and FIG. 10 shows an example block diagram of the relationshipbetween the component carriers and dedicated search spaces and crosscarrier scheduling with limited scheduling. The WTRU searches dedicatedsearch spaces or search space partitions for a PDCCH candidate forcomponent carriers (905). WTRU decodes PDCCH DCI formats with RNTIs(910) and determines if the DCI format has been correctly decoded (915).If not, the WTRU tries another CRC or RNTI (920). If all the DCI formatshave been correctly decoded, then for each correctly decoded DCI format,the WTRU uses the information with respect to where the PDCCH wasdetected to determine the relevant component carrier (925). WTRU thenuses the DCI information to receive the PDSCH or transmit the PUSCH(930). If additional search segments exist (932), the search (907) isthen repeated for the additional search space segments in the identifiedcomponent carrier using the same RNTIs (935). If all search segments arecomplete then additional dedicated search spaces or search spacepartitions for PDCCH candidates may be searched for other componentcarriers (940). Additional searches, for instance, are configurable. TheWTRU may be configured to search only in the control region of CC1. Inthis instance, the WTRU only searches CC1 SS, CC2 SS, CC3 SS and so on.Alternatively, the WTRU may be configured to search in control region ofother CCs such as CC2 or CC3. In this instance, the WTRU may continue tosearch CC1 SS, CC2 SS, CC3 SS in control regions of CC2, CC3 or both.The WTRU may receive configuration information from higher layersignalling e.g., RRC signalling and it may be WTRU specific. If the WTRUis configured to search only in the control region of CC1, thenscheduling flexibility is limited but PDCCH blind decoding complexitymay be reduced. If the WTRU is configured to search in control region ofmultiple CCs, then scheduling flexibility is increased at the cost ofhigher PDCCH blind decoding complexity. Alternatively, the WTRU maysearch the search spaces in a parallel fashion.

The DCI information may allow cross carrier scheduling such that the DCI(in the PDCCH) in a component carrier (say CC x) may schedule PDSCH (orPUSCH) in a different component carrier (say CC y), where CC x may notbe equal to CC y but in a limited fashion as shown in FIG. 10.

FIG. 10 shows the dedicated SS for CCs but with limited schedulingcapability. Cross carrier scheduling is limited in such way that a DCIin a CC (say CC x) can only schedule PDSCH (or PUSCH) in a different CC(say CC y) within a limited CC subset. For example, CC1 has informationwith respect to receiving PDSCH (or PUSCH) with respect to CC1 and CC2while CC3 has information with respect to receiving PDSCH (or PUSCH)with respect to CC3 and CC4.

The WTRU is semi-statically configured via higher layer signalling toreceive PDSCH data transmissions in a set of DL component carriers (sayCC1, CC2 as one set, and CC3, CC4 as another set as shown in FIG. 10)signalled via PDCCH transmitted in a specified or indicated DL componentcarrier (say CC1 in FIG. 8 or CC1, CC3 in FIG. 10) belonging to the saidset of DL component carriers or the said group of DL component carriers.The WTRU may not be required to receive PDSCH data transmissions in aset of DL component carriers signalled via PDCCH transmitted in a DLcomponent carrier not belonging to the said set of DL component carriersor the said group of DL component carriers.

The WTRU may monitor a set of PDCCH candidates for control informationin a specified or indicated DL component carrier belonging to the set ofcomponent carriers (say CC1, CC2 as one set, and CC3, CC4 as another setas shown in FIG. 10) or the group of component carriers (say CC1, CC2 asone group, and CC3, CC4 as another group in FIG. 10) in every non-DRXsubframe, where monitoring implies attempting to decode each of thePDCCHs in the PDCCH candidate set according to all the monitored DCIformats. The WTRU is not required to monitor a set of PDCCH candidatesfor control information in a DL component carrier that belongs to thedifferent set or group of component carriers. The WTRU is not requiredto monitor a set of PDCCH candidates for control information in a DLcomponent carrier that is not specified or indicated within the set orgroup of component carriers.

For FDD and normal HARQ operation, the WTRU shall upon detection of aPDCCH with uplink grant such as DCI format 0 and/or a PHICH transmissionin the set of DL component carriers in subframe n intended for the WTRU,adjust the corresponding PUSCH transmission in the set of UL componentcarriers that is linked with the set of DL component carriers insubframe n+4 according to the PDCCH and/or PHICH information that arereceived.

In another indication method, detection time may be used to indicatecomponent carriers. The time may be associated with the subframe orother specific time interval or period. The subframe in which a PDCCHmay be detected (in part or in whole) may determine the componentcarrier to be used with the allocation grant. The pattern mappingsubframe to component carrier may be cell specific or WTRU specific. Forexample, in subframes=0 mod 3, use component carrier c1, in subframes=1mod 3, use component carrier c2, and in subframes=2 mod 3, use componentcarrier c3.

In an alternative method, suppose there are up to K Orthogonal FrequencyDivision Multiplex (OFDM) symbols used in the DL for PDCCH (note thatK=3 in LTE). The network may map UL grant/DL assignment for up to Kcomponent carriers in K different OFDM symbols. Upon successful decodingof a PDCCH, the WTRU may determine the carrier index of the UL grant/DLassignment according to the time location (i.e., which OFDM symbol)within the downlink control region.

In another indication method, an explicit component carrier ID may beused to indicate component carriers. Bits may be inserted for carrier IDin a DCI format to indicate DL/UL component carriers. For example, 3bits may be used to represent 8 UL or DL component carriers.

In another indication method, scrambling sequence of the PDCCH may beused to indicate component carrier index. In LTE, PDCCH may be scrambledwith a sequence that is a function of cell ID and sub-frame index. Inthis embodiment, a scrambling sequence may used that is a function ofcell ID, sub-frame index and component carrier index to scramble PDCCHcarrying UL grant/DL assignment. Upon descrambling of the PDCCH, theWTRU may determine the component carrier index of the decoded ULgrant/DL assignment.

In another indication method, combinations of the methods describedherein may be used to indicate component carrier. As an example of acombination of the detection time and detection position method, K=3OFDM symbols may be used in the DL for PDCCH. Since there are no morethan 5 aggregated component carriers in each direction, the network mayconfigure 2 WTRU-specific search spaces for a particular WTRU. If aPDCCH (containing an assignment) is decoded by the WTRU in search spacei (i=1 or 2) and at OFDM symbol k (k=1, 2 or 3), then the WTRUdetermines the component carrier index according to a predeterminedmapping f(i,k). Other combinations or variations using the describedmethods herein are also possible.

In another unified method for DL assignment and UL grant, joint codingand joint transmission methods may be used. A single joint DL assignmentor UL grant is transmitted in the anchor or primary component carrier.In one approach, an explicit bitmap and/or special PDCCH may be used forthe assignment. In a first option, bits may be inserted in a DCI format(PDCCH) as a bitmap for each joint DL assignment or UL grant. In thisoption, ON or “1” means the component carrier has control informationand OFF or “0” means no control information. For example, a bitmap of“10101” may indicate that component carriers 1, 3 and 5 have controlinformation for DCI#1, 2 and 3, respectively. That is, the WTRU knowsthat three sets of DCI are available. This may be used in combinationwith a dynamic DCI format. To reduce blind format detection, the numberof component carriers may be signalled to the WTRU via PDCCH, RRC orhigher layer signalling. For example, if the number of DL componentcarriers and UL component carriers is known, the size of the DCI formatfor DL assignment and UL grant is known. If the number of DL and ULcomponent carriers is signalled via L1/2 control signalling, a specialPDCCH may be transmitted. The special PDCCH may carry the number of DLor UL component carriers and may be transmitted in certain subframes.For example, the special PDCCH may be transmitted in every M subframes,where M is configurable. Alternatively, some subframes may be configuredfor special PDCCH transmission. The special PDCCH may also carry bitmapsfor DL or UL component carriers and may be transmitted in certainsubframes as described previously.

In a second option using explicit bitmaps, RRC signalling or otherhigher layer signalling may carry bits as a bitmap for joint DLassignments or UL grants.

In a second method for joint coding and/or joint transmission, a staticDCI format may be used for the assignments. If the number of DL and ULcomponent carriers is not known or signalled, a static format may beused at the expense of higher overhead. In this case, the DCI format isfixed in length and no bitmap may be needed. Static DCI format andoverhead may be designed for a maximum number of component carriers, forexample, five component carriers. Alternatively, static DCI format andoverhead may be designed for some fixed number of component carriers,such as three component carriers, which is less than the maximum numberof component carriers.

A non-unified method for UL grant and DL assignment is described herein.Different methods may be used for UL grants and DL assignments. That is,one method may be used for DL assignment and another method may be usedfor UL grant. For example, separate coding/separate transmission may beused for DL assignment, and separate coding/joint transmission or jointcoding/joint transmission may be used for UL grant.

For DL assignment, separate coding/separate transmission with one-to-onemapping between DL component carrier and DL component carrier thattransmits the DL assignment may be used. For UL grant, separatecoding/joint transmission with RNTIs, such as those described herein,may be used to indicate UL component carriers. Alternatively, jointcoding/joint transmission with a bitmap indicating UL component carriersmay be used. Other combinations of methods described in the unifiedmethod may also be used.

Alternative UL and DL associations may also be used. The UL PDCCHcomponent carrier to UL-SCH component carrier pairing methods describedwhere z=x, z=f(y) or other described UL/DL alignment methods may also beapplied to other required UL/DL associations. For example, when a DL-SCHtransmission occurs, and UL hybrid automatic repeat request (HARQ)feedback indicating successful or unsuccessful transmission may need tobe transmitted, it may be necessary to know which UL component carriermay report the HARQ feedback for the DL-SCH transmission. Similarly whena UL-SCH transmission occurs, it may be necessary to know whichcomponent carrier DL HARQ feedback may be assigned to.

In another example, when the WTRU reports channel conditions or uplinkcontrol information such as channel quality indicator, precoding matrixindication, or rank indication (CQI/PMI/RI) on a PUCCH, it may benecessary to associate the DL component carrier with an UL componentcarrier carrying PUCCH.

The UL/DL carrier associations used for pairing DL PDCCH allocationswith UL-SCH transmissions may also be used to associate the UL/DLpairing of channel quality indicator (CPI), precoding matrix indicator(PMI), rank indicator (RI) or acknowledge/negative acknowledge(ACK/NACK) reporting. DL component carrier #x may be paired with ULcomponent carrier #y such that WTRU receives PDCCH in DL componentcarrier #x and transmits PUSCH in UL component carrier #y accordingly.UL component carrier #y may be used to report CQI, PMI, RI or ACK/NACKcorresponding to DL component carrier #x.

As described herein, the using of different RNTI addresses, such asC-RNTI or SPS-C-RNTI, to indicate to which uplink component carrier theDCI format may lead to, decreases the number of available RNTI that maybe shared among the WTRUs. Different approaches are described herein toshow how the network may share the different RNTI address across thedifferent frequencies among the different users.

The following describes how to reuse C-RNTI for PDCCH techniques incarrier aggregation such as separate PDCCH coding on a anchor/primarycomponent carrier; separate PDCCH coding on separate component carriers;and joint PDCCH coding on a anchor/primary component carrier.

In an example of separate PDCCH coding on a anchor/primary componentcarrier, it may be assumed that user one has an anchor component carrier1D with 1D, 2D, . . . X¹D and 1U, 2U, . . . , Y¹U component carrierswith assigned RNTIs: C-RNTI-1One, C-RNTI-2One, . . . , C-RNTI-Y1One, ifY¹ is larger than X¹ and user two has an anchor/primary componentcarrier 2D with 1D, 2D, . . . X²D and 1U, 2U, . . . , Y²U componentcarriers with assigned RNTIs: C-RNTI-1Two, C-RNTI-2Two, . . . ,CRNT-Y²Two, if Y² is larger than X².

Since the 2 users do not share the same search space as they are ondifferent anchor/primary component carriers, it shows that users on thesame anchor/primary component carrier must not share a RNTI. Therefore,a technique by which users are reassigned to other anchor componentcarriers may be useful not only for control region capacity loadbalancing but also in the context of sharing addresses. Also, dedicatedsignalling reassigning the anchor component carrier may include RNTIreassignment such as C-RNTI reassignment.

Described herein is a capacity analysis for this example. Assume a cellhas 5 component carriers in the uplink and 4 component carriers in thedownlink. C-RNTI being a 16 bit address, the network may thereforetheoretically assign 65536 C-RNTIs minus 2 addresses reserved for pagingRNTI (P-RNTI) and system information RNTI (SI-RNTI), or 65534. In thiscontext, the cell may assign equally up to 65564/5 users on eachdownlink component carrier or downlink anchor component carrier.Therefore, for the asymmetrical case where the number of anchorcomponent carriers (downlink) or downlink component carriers is largerthan the number of uplink component carriers, the cell may support up to65534 users. For the asymmetrical case, where the number of uplinkcomponent carriers is larger than the number of downlink componentcarriers, than the limit may be somewhat lower by a factor equal toNumber of DL component carriers/Number of UL component carriers. In ourcase, 80% of 65534 users.

Therefore, the usage of supplemental C-RNTI addresses to indicate towhich component carrier the DCI format applies to may not impact thenumber of theoretical users in a cell if an anchor component carrierapproach with separate coding is used. This theoretical analysis assumesall users are LTE-A capable and are pre-configured with the maximumnumber of aggregate component carriers in the uplink and the downlink inthe cell.

In an example of separate PDCCH coding on separate component carriers, afirst case assumes a full flexibility case, where the PDCCH received onany DL may map to any uplink component carrier. In this case, assumingthat user one has 1D, 2D, . . . X¹D and 1U, 2U, . . . , Y¹U componentcarriers with assigned RNTI: C-RNTI-1One, C-RNTI-2One, . . . ,CRNT-Y²One, if Y¹ is larger than X¹ and user two has 1D, 2D, . . . X²Dand 1U, 2U, . . . , Y²U component carriers with assigned RNTI:C-RNTI-1Two, C-RNTI-2Two, . . . , CRNT-Y²Two, if Y² is larger than X².In this context, since the WTRU-dedicated search space of user one anduser two may overlap on any downlink component carrier, addresses maynot be reused.

Described herein is a capacity analysis for this example. Assume a cellhas 5 component carriers in the uplink and 4 component carriers in thedownlink. C-RNTI being a 16 bit address, the network may thereforetheoretically assign 65536 C-RNTIs minus 2 addresses reserved for P-RNTIand SI-RNTI, or 65534. In this context, the cell may only assign up to65534/5 users in total in the cell.

A second case assumes a limited flexibility case, where the PDCCHreceives a component carrier that may map to one component carrier inthe uplink. In the case where more uplink component carriers areconfigured than in the downlink, a given downlink component carrier maybe assigned 2 or more addresses to differentiate DCI formats allocatedin the uplink. This theoretical analysis assumes all users are LTE-Acompatible and are pre-configured with the maximum number of aggregatecomponent carriers in the uplink and the downlink in the cell.

Described herein is a capacity analysis for this example. Assume a cellwith 4 downlink component carriers and 5 uplink component carriers. Onedownlink component carrier may be assigned an additional address. Inthis context, since each user needs 2 addresses to support thisasymmetrical case, the theoretical limit would be 65534/2 or65534/(number of uplink component carriers−number of downlink componentcarriers). This theoretical analysis assumes all users are LTE-Acompatible and are pre-configured with the maximum number of aggregatecomponent carriers in the uplink and the downlink in the cell.

In an example of joint PDCCH coding on a anchor/primary componentcarrier, joint PDCCH coding may support multiple assignments/grants todifferent component carriers with a common CRC, thus it cannot rely onthis method of using different C-RNTI or SPS-C-RNTI addresses toindicate to which uplink component carrier the DCI format is applicable.

Table 1 is a summary of the theoretical capacity analysis describedherein.

TABLE 1 PDCCH coding and assignment Theoretical user limit per cell A.Separate PDCCH coding on a anchor component 65534 * DL componentcarriers/UL carrier component carriers if UL > DL or 65534 B. SeparatePDCCH coding on separate component 65534/UL component carrierscarriers - Full flexible case (case 1) B. Separate PDCCH coding onseparate component 65534/(UL component carriers-DL carriers - Notflexible case (case 2) component carriers) if UL > DL or 65534 C. JointCoding Not applicable, cannot rely on this technique

This theoretical analysis assumes all users are LTE-A compatible and arepre-configured with the maximum number of aggregate component carriersin the uplink and the downlink in the cell. Also, no SPS-C-RNTI may beallocated.

While the present invention has been described in terms of the preferredembodiment, other variations which are within the scope of the inventionwill be apparent to those skilled in the art.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A wireless transmit receive unit (WTRU) thatcommunicates using orthogonal frequency division multiplexing (OFDM),the WTRU comprising: a receiver; and a processor; the processor andreceiver configured to: receive an indication of one or more searchspaces for one or more physical downlink control channel (PDCCH)candidates and an indication of a downlink control information (DCI)format of a plurality of DCI formats for each search space of the one ormore search spaces; monitor, in the one or more search spaces, the oneor more PDCCH candidates having the respective DCI format; and receiveDCI associated with a user identity of the WTRU via at least one PDCCHtransmission.
 2. The WTRU of claim 1, wherein the processor and receiverare further configured to receive data via at least one physicaldownlink shared channel (PDSCH) transmission indicated by the at leastone PDCCH transmission.
 3. The WTRU of claim 2, wherein OFDM subcarriersvia which to receive the data are indicated by the at least one PDCCHtransmission.
 4. The WTRU of claim 1, wherein a first DCI format of theplurality of DCI formats includes a carrier indicator that indicates acarrier via which a physical downlink shared channel (PDSCH)transmission is to be received.
 5. The WTRU of claim 4, wherein the atleast one PDCCH transmission is received with the first DCI format via afirst carrier and the carrier indicator indicates a second carrier. 6.The WTRU of claim 4, wherein a second DCI format of the plurality of DCIformats does not include a carrier indicator.
 7. The WTRU of claim 6,wherein the second DCI format has fewer bits that the first DCI format.8. The WTRU of claim 6, wherein the first DCI format is associated witha first search space and the second DCI format is associated with asecond search space.
 9. The WRU of claim 1, wherein the processor andreceiver are further configured to receive a first PDCCH transmissionvia a first carrier and to receive a second PDCCH transmission via asecond carrier.
 10. The WTRU of claim 1, wherein the one or more searchspaces includes a user specific search space.
 11. A method performed bya wireless transmit receive unit (WTRU) that communicates usingorthogonal frequency division multiplexing (OFDM), the methodcomprising: receiving an indication of one or more search spaces for oneor more physical downlink control channel (PDCCH) candidates and anindication of a downlink control information (DCI) format of a pluralityof DCI formats for each search space of the one or more search spaces;monitoring, in the one or more search spaces, the one or more PDCCHcandidates having the respective DCI format; and receiving DCIassociated with a user identity of the WTRU via at least one PDCCHtransmission.
 12. The method of claim 11, further comprising receivingdata via at least one physical downlink shared channel (PDSCH)transmission indicated by the at least one PDCCH transmission.
 13. Themethod of claim 12, wherein OFDM subcarriers via which to receive thedata are indicated by the at least one PDCCH transmission.
 14. Themethod of claim 11, wherein a first DCI format of the plurality of DCIformats includes a carrier indicator that indicates a carrier via whicha physical downlink shared channel (PDSCH) transmission is to bereceived.
 15. The method of claim 14, wherein the at least one PDCCHtransmission is received with the first DCI format via a first carrierand the carrier indicator indicates a second carrier.
 16. The method ofclaim 14, wherein a second DCI format of the plurality of DCI formatsdoes not include a carrier indicator.
 17. The method of claim 16,wherein the second DCI format has fewer bits that the first DCI format.18. The method of claim 16, wherein the first DCI format is associatedwith a first search space and the second DCI format is associated with asecond search space.
 19. The method of claim 11, further comprisingreceiving a first PDCCH transmission via a first carrier and receiving asecond PDCCH transmission via a second carrier.
 20. The method of claim11, wherein the one or more search spaces includes a user specificsearch space.